Traditionally an ophthalmic device, such as a contact lens included a biocompatible material with a corrective, cosmetic or therapeutic quality. A contact lens, for example, can provide one or more of: vision correcting functionality; cosmetic enhancement; and therapeutic effects. Each function is provided by a physical characteristic of the lens. A design incorporating a refractive quality into a lens can provide a vision corrective function. A pigment incorporated into the lens can provide a cosmetic enhancement. An active agent incorporated into a lens can provide a therapeutic functionality.
The sensitive nature of an ophthalmic area on a human has resulted in comfort being an important characteristic of a lens. Various lens materials are often associated with varying levels of comfort. In addition, an industry has been developed for ophthalmic drops and additives to lenses to address the comfort issue.
Another important quality of a lens is the optical quality of a lens which influences how well an ophthalmic lens wearer will see while wearing a particular lens. Traditionally, a lens material as well as a lens design may affect the experience of an ophthalmic lens wearer while utilizing the lenses.
Although an experience of wearing ophthalmic lenses has made advancements in regard to comfort and optical quality, there still exists a need to further improve the experience of an ophthalmic lens wearer. New materials and ophthalmic solutions introduce many variables which are not always easy to quantify. In addition, new materials and solutions, although beneficial, often require significant amounts of time and resources in order to receive government approvals and be presented to a lens wearer.
Some designs of contact lenses have included different characteristics of a convex surface and a concave surface. For example, it has been known to have a contact lens with one radius of curvature on each of the front optical surface and another radius of curvature on the back surface of the lens. One disadvantage of this prior art approach is that light rays passing through the peripheral areas of the lens tend to focus in the eye in front of those passing through the center of the lens. This prior art approach restricts its depth-of-focus or field, and the quality of the optical image formed.
Other prior art examples include a multifocal contact lens having a spherical curve in the center region of the concave surface and an aspheric curve which surrounds the center spherical region. A disadvantage of this contact lens design is the use of corrective aspheric radii, which are difficult to measure and manufacture in practice.